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Failing in this, he found what till then was unknown, that sulphuret of baryta would "absorb the sun's rays by day, to emit them by night."

Thus Dana says: "Merely the rapid motion of a feather across some specimens of sulphuret of zinc will often elicit light more or less intense from this metal."

In many cases, where one of these is excited all the others are set in motion: thus when sulphuret of antimony is electrified, at the moment of electrization it becomes magnetic; at the same time it is heated; if the heat is raised to a certain intensity, light is produced; the compound is decomposed, and chemical action is thereby brought into play; and so on.

To soften stoppers which have already become hardened, they should be brought together in a jar with sulphuret of carbon until they are pliable and afterward kept as recommended above.

The latter, on an egg being eaten on a silver spoon, stains the spoon of a blackish purple, by combining with the silver, and forming sulphuret of silver.